1. Field of the Invention
The invention relates to the twisted pair cable, and particularly to the cable having a bundle of twisted pairs of conductors.
2. The Related Art
U.S. Pat. No. 6,348,651 with the same applicant and the same assignee, discloses an approach to implement low crosstalk of a flat cable having a plurality of twisted pairs (of conductors) closely side by side arranged one another. The arrangement of those plural twisted pairs is essentially concerned about a two dimensional design. Anyhow, sometimes the conductors of the cable is required to be of a bundle type in some applications. In other words, a three dimensional arrangement among the twisted pairs of conductors is required to implement the low crosstalk. U.S. Pat. No. 6,355,876 ('876 patent) discloses an approach to lower the crosstalk. Anyhow, even though the '876 patent tries to introduce a unique way to replace the traditional random trial-and error method for a better result, differentiation of the pitch among different pairs seems still unsystematic and complicated in manufacturing. The two self-twisted pairs require to be further mutually tangled/interleaved with each other. The varied pairs may cause some non-uniform impedance and propagation delay. The cross cancellation among the twisted pairs requires the common-integer turns, thus taking a longer distance for implementation of such crosstalk cancellation. It questionably fits the high frequency, and still needs another trial-and-error to figure out the lay variations, (referring to different pitches of the different twisted pairs mentioned in column 5, lines 41–57). Additionally, the four twisted pairs as disposed in FIG. 2 of the '876 patent, can be not densely/compactly/evenly arranged with one another, thus taking much space.
An object of the invention is to provide a scientific, systematic, and easy way to lower the crosstalk among the three dimensionally arranged twisted pairs of conductors.
In the aforementioned applicant's previous patent, i.e., U.S. Pat. No. 6,348,651 ('651 patent), it is proved that the twisted pairs with different/opposite twisting directions may each other cancel out the crosstalk noise with around a ninety degrees phase shift where the phase shift is calculated from the offset of the twist starting point or node point between the adjacent pairs, referring to FIG. 2A. Thus, under a controlled/precise manner, the shift angle is expected to be equal to 360 * offset (distance)/the twist pitch, as shown in FIG. 1. It is noted that the '651 patent discloses the adjacent two twisted pairs having the opposite twist directions (i.e., clockwise and counterclockwise) because it is derived from FIG. 2 of the '651 patent which is an advanced design relative of FIG. 1 of the '651 patent wherein the two adjacent twisted pairs have the same twist direction (i.e., either clockwise or counterclockwise). Anyhow, the same technology, i.e., the ninety degrees phase shift was considered to be also applicable to the cable shown in FIG. 1 of the '651 patent with the same result (referring to FIG. 2B), except that the radiation/field of the cable in FIG. 2 of the '651 patent may be deemed eliminated due to opposite twist directions between every adjacent two twisted pairs while that of the cable in FIG. 1 of the '651 patent may be accumulated larger due to the same twist direction between every adjacent two twisted pairs without roughly the field cancellation benefit at the far end of the cable.
The copending parent application Ser. No. 10/229,640 discloses a three-dimensional arrangement of a bundle of twisted-pair cable essentially composed of a plurality of twisted differential pairs arranged in a quadrate manner among the neighboring pairs. Anyhow, such a quadrate arrangement is not a densest one of the bundle of twisted pairs. In fact, a hexagonal compact package for such twisted pairs can achieve the most compact size.